How could wormholes transport us through time?

What?

Wormholes – not the type made by insect larvae burrowing in rotting wood – are common in science fiction as an unpredictable method of time travel. As we’ve seen in many other examples, science fiction often involves concepts that have been proven to be scientifically impossible. However, this concept finds some traction with scientific principles.

Why?

J.J. Abrams’ 2009 Star Trek movie featured Spock and a Romulan ship falling through a wormhole that sent them back in time 129 years.

The Romulan ship coming out of the wormhole in Star Trek (2009)

In The Avengers, the Tesseract, a powerful mythical artifact, opened a wormhole in space, allowing the alien Chitauri to invade New York City (because every alien invasion just has to take place in New York City…).

Chitauri ships coming in through the portal in The Avengers (2012)

The Doctor in Doctor Who travels through a “time vortex” that transports his time machine, the TARDIS – which takes the form of a blue British police telephone box – to any point in time and space.

The TARDIS flying through the time vortex in Doctor Who (2005)

Wormholes are at the base of many, many examples of fictional interstellar time and space travel. By understanding their mechanisms, perhaps we can figure out a way to make science fiction into reality.

How?

Wormholes are technically known as Einstein-Rosen bridges in honor of physicists Albert Einstein and Nathan Rosen who first proposed their existence. This was initially based off of Einstein’s theory of special relativity, formulated in 1905 and comprised of two parts:

1) The distance (d) traveled depends on how fast you move (velocity) and for how long you’re in motion (time). An easy example of this is if you drive 55 mi/hour for one hour, then you travel 55 miles.

2) The speed of light is the same for all observers, whether or not they’re in motion. This means that people will experience light the same way whether they’re in a rocket traveling 28,000 km/hour, driving a car at 55 mi/hour, or standing still.

When these two ideas are taken together, we come to Einstein’s conclusion that space and time are relative and are actually so interconnected that they create a single continuum known as space-time.

Einstein then began attempting to expand this theory into a theory of general relativity to involve acceleration (until then, Einstein’s theory only considered objects in constant, non-accelerating motion and objects at rest). As he was working out the equations, though, he realized that massive objects cause a distortion in the space-time continuum. Two massive objects, such as the sun and Earth, can exert a force of attraction on one another known as gravity,the way that the sun pulls the Earth toward it in orbit.

Imagine that a large, heavy object – a TV set or something – is placed in the center of a trampoline. The object presses down into the surface of the trampoline, creating a large dimple. If a marble is rolled around the edge of the trampoline, it would spiral inward toward the TV in the same way that the gravity of the sun pulls at the planets in the solar system (Redd). The two dimensions of the trampoline’s surface represent the two dimensions of space and time, warped by gravity.

Einstein and Rosen then proposed that bridges could be made from one point in space-time to another, creating a “shortcut” between two different times and distances. Imagine that we have two dimples in space-time represented by the trampoline. One dimple is on the right half, the other is on the left half. If the trampoline is curved over itself, rather than laid flat out on the ground, then these two dimples would actually become much closer to each other and could be stacked one right on top of the other.

If these masses are large enough, the dimples could become so deep that they end up meeting, creating a tunnel from one point in space-time to another – a wormhole! (Bonsor).

So?

The predicted Einstein-Rosen bridges would be impossible to travel through because they would be incredibly unstable, collapsing too quickly for something to travel through to the other side. Furthermore, this is only a simplified visualization. Wormholes would also be impossible to visually detect (and depict) because the space-time continuum doesn’t consist of merely two dimensions. Theories state that the space-time continuum actually ought to consist of at least 4 dimensions (time + our three dimensions of height, width, and depth) at the minimum.

Recent research, though, has determined that wormholes containing “exotic” matter have the potential to stay open for longer periods of time. Exotic matter contains negative energy density and negative pressure, features that are related to the inherent fluctuations of energy in any energy or magnetic field. This has previously only been seen in certain vacuum states as part of quantum field theory, explaining why wormholes as of now have only been postulated to exist in quantum foam, the smallest environment in the universe.

Adding exotic matter to these wormholes might be able to provide enough stability to allow humans to pass safely through, but even the introduction of regular matter could cause the tunnel to collapse (Redd). It looks like for now, we’ll have to search for alternative ways of time travel. Has anyone seen a blue police box flying through the sky lately?